1. Field of the Invention
The present invention relates generally to spray polyurea elastomers and, more specifically, to spray polyurea elastomers which include chemically sized mineral particles, thereby improving the abrasion resistance of the cured elastomer.
2. Description of Background Art
Elastomer systems are commonly recognized as, among other things, coating materials, with spray polyurea elastomer systems being particularly useful when employed in this capacity. One of the considerations confronting the skilled artisan is the abrasion resistance of the coating after it is ultimately applied to a substrate. In accordance with the present invention the abrasion resistance of a spray polyurea elastomer is improved by incorporating chemically sized mineral particles in the system as is discussed with particularity hereinbelow.
U.S. Pat. No. 4,585,850 describes a reaction injection molded (RIM) elastomer made by reacting, in a closed mold, an amine terminated polyether of greater than 1500 average molecular weight, having greater than 50% of their active hydrogens in the form of amine hydrogens; a chain extender; flaked glass pretreated with an amino silane coupling agent; and an aromatic polyisocyanate. The '850 patent referred to above contains a discussion of other applications and patents in the field; for example, U.S. Pat. Nos. 4,474,900 and 4,507,090, and is incorporated herein by reference. Similarly, U.S. Pat. No. 4,716,193 describes a reactive glass component employed in a reinforced reaction injection molded elastomer. However, since these patents relate to RIM elastomers, patentees are not concerned with abrasion resistance. Specifically, RIM articles are invariably formed in a closed mold and, accordingly, the elastomeric material used to form the molded article becomes pressurized within the mold as additional amounts of elastomer are introduced therein. As a result, the density of the thus formed article is greater at the locus of the surface or skin, relative to the density at the locus of the core. The increased surface density of a RIM article provides a characteristic resistance to abrasion. This phenomenon is not exhibited by spray polyurea coatings, inasmuch as the coating is sprayed onto a substrate, i.e., an open mold, and, accordingly, the pressure required to provide the increased surface density is unavailable.
Furthermore, since the article formed via RIM typically has a topcoat, the degree to which the RIM article exhibits resistance to abrasion is even further enhanced.
U.S. Pat. No. 3,979,364 describes the use of aminated polyethers as hereinafter used as a component with a polyol to make an elastomer. U.S. Pat. No. 3,666,788 describes the use of cyanoalkylated aminated polyethers in spray systems. The '788 disclosure, in Column states that the aminated polyethers as used hereinafter cannot be used in spray coatings due to very rapid reaction rates with isocyanates.
U.S. Pat. Nos. 4,379,729; 4,444,910 and 4,433,067 describe elastomers which are prepared using a high molecular weight amine terminated polyether, an aromatic diamine chain extender and an aromatic polyisocyanate which may merely be a polyisocyanate or a quasi-prepolymer prepared from a polyol reacted with a polyisocyanate wherein some isocyanate groups are still left unreacted. Various patents have been applied for and received using the basic combination recited above as well as various mold release agents and other additives, such as catalysts and fillers, including glass fibers. For example, see U.S. Pat. No. 4,607,090.
Polyoxyalkylene polyamines, particularly JEFFAMINE.RTM. T-403, D-400 and D-230, are described as chain extenders in U.S. Pat. No. 4,732,919; however, this patent relates to an elastomer system to be used in a RIM application.
The publication "Silane Effects and Machine Processing in reinforced High Modulus RIM urethane Composites," by E. G. Schwartz, et al., Journal of Elastomers and Plastics, vol. 11 (October, 1979), page 280, describes the use of silane treated milled glass fibers in reinforced RIM composites.
The publication "Surface Modification for RRIM Urethanes," by Ed Galli, Plastics Compounding (Jan/Feb 1982) describes silane treated glass fiber reinforcement of RRIM urethanes.
Commonly assigned U.S. patent application Ser. No. 261,193 describes spray polyurea elastomers which include roved filler materials that are externally added. A method for making those elastomers is also described.
Therefore, it is my understanding that a spray polyurea elastomer system which includes chemically sized filler materials incorporated directly in the elastomer and which exhibits favorable resistance to abrasion, especially when employed as a coating, has heretofore been unavailable.